Comprehensive Income (Reclassification out of other comprehensive income) (Details) - USD ($) $ in Millions	3 Months Ended
	Oct. 29, 2016	Oct. 24, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total amounts reclassified out of AOCI	$ 3	$ (5)
Cumulative translation adjustment and actuarial gains and losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
(Gains) losses reclassified out of AOCI	0	(1)
Reclassification out of Accumulated Other Comprehensive Income | Net unrealized gains and losses on available-for-sale investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other income (loss), net	15	(1)
Reclassification out of Accumulated Other Comprehensive Income | Net unrealized gains and losses on cash flow hedging instruments | Cash Flow Hedging
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Operating expenses	(9)	(2)
Cost of sales—service	(3)	(1)
Net unrealized gains and losses on cash flow hedging instruments	$ (12)	$ (3)